Method of waterproofing cellulosic materials and product thereof



T. RAPHAEL ET AL 3,039,915 METHOD OF WATERPROOFING CELLULOSIC MATERIALSAND PRODUCT THEREOF Filed Jan. 22, 1959 FIG. I

P-TERTlARY-BUTYL PHENOL CONDENSED WITH FORMALDEHYDE CONDENSED WITHFORMALDEHYDE '1; RESIN BASED ON FIBER WEIGHT INVENTORS THOMAS RAPHAELLAURENCE R-B. HERVE! 3 WATER ABSORPTION P-NOm PHENOL zo Em m 253 65 June19, 1962 ATTORNEY 3,039,915 Patented June 19, 1962 ice 3,039,915MtETl'iOl) OF WATERPRGGFING CELLULGSIC MATERIALS AND PROBUCT THEREOFThomas Raphael, VJinchester, and Laurence R. B. Hervey, West Concord,Mass, assignors to Arthur 1). Little, Inc, Cambridge, Mass, acorporation of Massachusetts Filed Jan. 22, 1959, Ser. No. 788,368 13Claims. (Ql. 162--165) This invention relates to a process forwaterproofing paper and the resulting waterproofed paper.

In many applications it is desirable to have available a waterproofpaper which will absorb only a small amount of water even whencompletely immersed in it for extended periods. Among such applicationsmay be cited the use of waterproof paper as insulating material insplashproof electric motors. Paper which is to be used in thisapplication should exhibit a minimum water pickup, at the same time havea maximum dielectric strength even after extended periods of exposure towater, and

still be flexible enough to be folded through 180 without cracking. Thismeans that a paper must be treated in such a way as to be capable ofpreventing the passage of an electric current therethrough even whenwet. It is customary to use relatively dense paper as insulation insplashproof motors and hence the normal technique of saturating thepaper by immersing it in a waterproofing composition is notsatisfactory.

A number of methods have been developed in the past to render cellulosicmaterials and more particularly highdensity papers waterproof. Suchmethods have included impregnating the paper with a resin such asphenolformaldehyde or treating the paper with aluminum acetate andparaffin wax, the stearato-chrome complexes or with silicone treatingagents. None of these treatments has produced entirely satisfactorywaterproof paper. The introduction of resins in sufficient quantities toadequately waterproof the paper has resulted, in most cases, in theproduction of a very stiif and brittle material. Moreover papers thuswaterproofed may assume the physical characteristics of the resins andlose most of their characteristics as paper. The other treatmentsmentioned have not resulted in the formation of waterproof papers whichpossess good wet dielectric strength throughout. Thus, for example, ifthe waterproof paper is somewhat spotty it means that certain sectionsof it will exhibit no dielectric strength and hence make the entirepaper unsatisfactory as an insulation.

Many of the treatments for waterproofing paper in the prior art havetended to concentrate their waterproofing effects on the outside surfaceof the paper. This is not desirable for the production of a paper whichshould exhibit a high dielectric strength, for it is necessary that thepaper possess good wet dielectric strength throughout.

Moreover, limiting a treatment to the surface means that there exists apossibility of lateral leakage, especially if the paper is cutsubsequent to treatment. In contrast, the treatment according to thisinvention provides the possibility of adding the treating materialduring paper formation, hence achieving a uniform treatment throughout t16 entire thickness of the paper.

It would therefore be desirable to have a waterproof paper (and areliable method for making it) which does not absorb any substantialamount of water and which is capable of exhibiting high dielectricstrength even after prolonged immersion in water.

it is therefore an object of this invention to provide a flexiblewaterproof paper which absorbs only a minor amount of water even whenfully immersed, and which at the same time retains its othercharacteristics as a paper. It is another object to provide a waterproofpaper which exhibits a good dielectric strength even when immersed inwater. Another object is to provide a method for waterproofing paper toimpart to it high dielectric strength without materially decreasing itsflexibility or depriving it of its other inherent paper or cellulosiccharacteristics.

It is yet another object of this invention to provide a paper which isuniformly treated throughout its entire thickness and which is notsubject to lateral leakages. These and other objects will becomeapparent in the following description.

By the process of this invention paper is waterproofed and made to havegood dielectric strength even after prolonged exposure to Watercharacterized by the step of adding to the paper making stock a resin inthe form of a water-alcohol or an alcohol solution. The material whichis added to the paper making stock may be defined as a solution of acondensation resin formed by condensing substituted phenols with aformaldehyde source to form a resin which is soluble in acetone and thelower alcohols. More particularly, the waterproofing material may bedefined as a solution of a condensation resin formed by reacting aformaldehyde source and a substituted phenol under refluxing conditionsto form a condensation resin soluble in acetone. The substituted phenolmust have substituent radicals so placed that not more than two methylolradicals can be added to the substituted phenol. The substituentradicals are selected from a group consisting of saturated andunsaturated aliphatic radicals having a total of between 4 and 12 carbonatoms and saturated and unsaturated cyclic hydrocarbon groups which whenjoined to the phenolic ring do not result in a compound havingconjugated unsaturation throughout. The resin solution which is added tothe paper stock contains from about 15 to about 35 resin solidsdissolved in a mixture of a lower alcohol and water along with astrongly alkaline material present in a, concentration equivalent fromabout 0.05 to about one mol of the alkaline material for each mol of thesubstituted phenol in the condensation resin.

By the process of this invention this solution of condensation resin isdispersed in the paper stock to form what may be essentially describedas an emulsion whereby the resin solution forms the discontinuous phaseand is present in droplets probably of colloidal dimensions.

In a copending application, Serial No. 788,369, filed January 22, 1959,there is disclosed the use of condensation resin products formed whencertain substituted phenols are reacted with a formaldehyde source, putinto solution and the solution applied to fibers and fabrics of naturalor synthetic origin whether by immersion or sur-.

face coating.

This invention will be described in detail and with reference to theaccompanying drawings in which:

FIG. 1 shows the relationship between the amount of condensation resinin the paper and the amount of water absorbed, the resin having beenadded in accordance with this invention; and

H6. 2 shows the relationship between the amount of water absorbed andthe wet dielectric strength of the resulting treated paper.

The condensation resin and its formation is first described and then themanner in which it is added to the paper stock is set forth.

The condensation resin product suitable for this invention is one whichis formed by reacting a substituted phenol and a source of formaldehyde.The phenolic compound suitable fcr forming the condensation resin usedin waterproofing according to the practice of this invention may be amonoor di-substituted phenol, and the substituent groups may be in theortho or para portions. The substituents may be saturated or unsaturatedaliphatic groups having from 4 to 12 carbon atoms; or they may besaturated or unsaturated cyclic groupings as long as such groupings donot result in the formation of a compound having conjugated unsaturationthroughout its structure. 'If the phenol has two aliphatic substituents,the total number of carbon atoms in the two substituents should not beless than 4 nor greater than 12. Beyond the limit of a total of 12carbon atoms the condensation reaction is extremely slow at thetemperatures employed in forming the resin, while the methyl substitutedphenols (monoor di-) give a resin which when used in accordance withthis invention is not adaptable to beater addition, and which results inundue embrittlement of the treated material. Monoethyland thepropyl-substituted phenols are not known, at least they are notcommercially available chemicals.

With regard to the cyclic substituents, it appears that if the resultingsubstituted phenol has conjugated unsaturation throughout (such as wouldresult for example in the use of para-phenyl-phenol) there would occuractive groups on the substituent which would interfere with thecondensation reaction.

The substituted phenol may then generally be defined as a phenol havingsubstituent radicals so placed thatone 'or two -CH OH groups supplied bythe formaldehyde source may add to the phenol structure. The substituentradical groups on the phenol are selected from the group consisting ofsaturated and unsaturated aliphatic radicals having from 4 to 12 carbonatoms in any one aliphatic radical and from 4 to 12 total carbon atomsin two aliphatic radicals, and saturated and unsaturated cyclichydrocarbon radicals which when joined to the phenolic ring do notresult in the formation of a compound having conjugated unsaturationthroughout.

This definition of the substituted phenols suitable for the practice ofthis invention eliminates theuse of monomethyl substituted phenol(cresol) and of dimethyl phenol as well as monoethyl and the propylsubstituted phenols. As pointed out above, the use of these results inexcessive embrittlement of the material treated, and resins made withthem are not suitable for beater addition. This definition thereforeincludes mono-substituted phenols having aliphatic substituents rangingfrom butyl to dodecyl and di-substituted phenols having aliphaticsubstituents ranging from diethyl to dihexyl. There appears to be alinear relationship between the chain length of the substituent group,in the case of aliphatics, and the final degree or" waterproofingachieved. This linear relationship extends to propyl substituents butnot to methyl, a fact which is in accordance with the usual differencesin behavior existing between the first members of a homologous seriesand the higher members of the same group.

The source of formaldehyde may include formalde- -hyde,paraformaldehyde, trioxymethylene, hexamethylenetetramine or any othercompound which will readily liberate formaldehyde at temperatures underabout 200 F. It has been found that the higher aldehydes such asbutyraldehyde and acetaldehyde are not practical reactants for thiscondensation reaction since the reaction does not proceed at anyreasonable rate at the temperatures preferably employed.

In forming a condensation resin suitable for waterproofing paper inaccordance with this invention it is necessary to form a resinousmaterial which will, unlike normal phenol-formaldehyde resins, permitthe paper to remain flexible. Therefore, the choice of the substitutedphenol used in forming the condensation resin is important and to bedistinguished from the phenol normally used in formingphenol-formaldehyde resins and from a mixture of substituted phenols andsubstantial amounts of unsubstituted phenols.

By substantial amounts of unsubstituted phenols is meant thosequantities which will material effect the physical characteristics ofthe material, e.g., paper. Limiting 'the quantity of unsubstitutedphenols does not, of course, preclude the incorporation of additivessuch as groups to the substituted phenol in ortho and/or para positions(the meta position will not react with formaldehyde). The possiblernono-tunctional substituted phenols may be represented by V on OH lX-@R BUR l a l R X while di-functional substituted phenols may herepresented by olH 0H x0): XO-R i where R represents the substituentradical as defined above and X represents the possible positions wherethe methylol group from the formaldehyde source may attach.

When di-functional phenols are used in the condensation reaction to formthe paper-treating composition of this invention, the molar ratio offormaldehyde to substituted phenol may vary from about 2:1 to about 1:1.In reactions where mono-functional phenols are employed, this molarratio may range from about 0.5 :1 to about 1:1.

The condensation product which is used to waterproof the paper inaccordance with the practice of this invention is prepared prior to itsincorporation into the paper. The product is generally a viscousmaterial and condensation is preferably carried out under moderateconditions of temperature and for periods which result in a resin whichremains soluble in the lower alcohols and in acetone.

Moderate temperature conditions in the process of this invention may befurther defined as ranging from about F. to about 200 F. Condensationreactions car-,

ried out at room temperature do not give as satisfactory condensationproducts (with respect to waterproofing in this invention) as thosecarried out within the range specified. It is important that the finalcondensation resin to be used be soluble in acetone, for if it iscarried out to the point where it is no longer soluble in acetone theresulting resin is not suitable for the treatment of paper to obtain theresults desired.

In general the condensation product is formed by mixing the substitutedphenol, the source of formaldehyde, a suitable catalyst and one of thelower alcohols, along with some water if desired. This mixture is thenrefluxed for a period ranging from about one-half to ten hours and at atemperature preferably below about 200 F., but above about 150 F. Thetemperature and time may be varied Within these limits as long as theresulting condensation product remains soluble in acetone.

In the formation of the condensation product either an acidic or basiccatalyst may be used. For example, it has been found equally acceptableto use strong bases such as sodium hydroxide, a milder base such ascalcium hydroxide, or an acid such as hydrochloric. This wide choice ofcatalyst is apparently due to the nature of the linkages formed in thecondensation reaction, i.e., few, if any cross-linkages are formed.Although it would probably be possible to achieve the requiredcondensation reaction without a catalyst, the catalyst is preferable ifthe reaction is to take place in a reasonable length of time in therequired temperature range.

The condensation product resulting from the reaction of this inventionmay be handled in one of two ways. After the product has been formed itmay be washed with water and then redissolved in a suitable solvent(acetone or the lower alcohols with or without some water) prior to itsintroduction into the paper stock. It is preferable, however, to use thereaction product as it is formed since it is not necessary to wash itand redissolve it. In this case, as will be seen in the followingdescription, it is preferable to employ a strongly alkaline material forthe reaction catalyst.

In any case the final resin which is added to the paper stock before itis laid must be a true solution of the condensation product made up inone of the lower alcohols or in acetone (usually along with some Water)as a solvent. Moreover, the solution must contain from about 0.05 toabout one mol of a strongly alkaline material (preferably sodiumhydroxide) for each mol of substituted phenol present in the resin. ifthe concentration of the strongly alkaline material is less than theminimum specified, the resin will not be efiective as a waterproofingagent; while if quantities which are substantially greater than thatspecified are used, the excess may impair some of the characteristics(e.g., dielectric strength) of the finally treated paper.

The solution which is added to the paper stock may also contain a smallamount of water as long as none of the resin is precipitated out. Thewater may be added to reduce the cost of the resin solution. lt ispossible that water also causes a somewhat more rapid dispersion of theresin into the fiber stock. In determining the amount of water which canbe added to the resin solution it is preferable to allow a margin ofsafety to compensate for alcohol evaporation and the like. The margin ofsafety may easily be determined by titrating a sample of resin dissolvedin alcohol with water. Water tolerance of the resin is indicated when amilkiness is developed.

The requirement for the addition of the strongly alkaline material inthe resin solution which is added to the paper stock makes it preferableto use a strongly alkaline material as the catalyst in the formation ofthe condensation resin, but as pointed out above, other catalysts aresuitable in the actual formation of the resin.

The resin solution which is to be added to the paper stock may befurther characterized as an alcohol, wateralcohol, acetone, orWater-acetone solution of the resin condensation product in which theresin is present in concentrations equivalent to from about to about 35%by weight resin solids with a preferable range from about to about Ifthe resin is present in concentrations over about 35 it is difficult toget it properly dispersed on the paper fibers. If, on the otherhand,solutions are used in which the resin is present in less than about 15%,there results a waste of solvent. The resin solution may further becharacterized by the fact that it must contain from about 0.05 to aboutone mol of a strongly alkaline material for each mol of substitutedphenol. Water may also be present in the solution in a quantity belowthat at which any of the resin will precipitate.

In order to make a dense paper with a good dielectric strength it isnecessary to have the waterproofing material thoroughly and equallydistributed throughout the en ire thickness of the paper. Thewaterproofing material must also be deposited on the individual fibersin a Way to chest maximum protection against the water. Gooddistribution and maximum protection are achieved by the resins of thisinvention and by the process by which these resins are applied.

The mechanism by which the process of this invention actually functionsmay not be fully understood. It is,

however, known that it is necessary to disperse the resin solution inthe paper stock in the form of very fine droplets, many of which areapparently of colloidal dimensious. in order to do this it appearsnecessary to introduce the resin in the form of a solution and to forman emulsion of the resin in the paper stock so that the resin solutionis in efiect the discontinuous phase and the water in the stock is thecontinuous phase. To form this type of emulsion it appears necessary tomake up the'resin solution with sufiicient alcohol and a stronglyalkaline material to furnish hydrophillic groups at the interfacebetween the resin droplets and the water of the paper stock. When anexhausting agent is subsequently added the interface is broken and theresin in the solution is irnrnediatel attracted to the cellulosicfibers. It is believed that the role of the alcohol and the stronglyalkaline material in the resin solution is one of furnishing theserequired hydrophillic groups.

The resin solution, as defined above, may be added to the paper stock atany point in the paper-making process before the actual formation of thepaper, i.e., before the stock enters the paper machine. That is, it maybe added in the beater, in the stock chest, or to the stock stream asproceeds to the paper machine. It is, however, preferable to add theresin in the beater inasmuch as it has been found that some agitation ofthe stock after resin addition achieves better mixing and betterdistribution of the resin on the fibers in the exhausting process.

()nce the resin has been added to the paper stock and after the solutionhas been thoroughly dispersed to form the necessary emulsion, it isnecessary to exhaust out the resin on the fibers. This is done by addingan acid to the stock before it gets on the paper machine. The acid actsto break the emulsion and deposit the resin on the fibers. The acid ispreferably introduced in the form of so-called paper makers alum(aluminum sulfate). This acid material is particularly well suited tothe process of this invention because of the tendency of the trivalentaluminum ion to precipitate the resin and deposit it on the fibers. Thisis due to the electrostatic attraction which cellulose has for thealuminum ion. However, other acids such as acetic acid or a small amountof a strong mineral acid may be used.

The amount of resin or condensation product which is taken up by thepaper to waterproof it in accordance with this invention may be variedfrom about 2 to about 40% by weight of the fiber in the paper. Thepreferred amount of resin pickup is from about 3 to 12% by fiber weight.Generally from about to about of the resin present in the stock is takenup by the fibers. The amount of resin which must be added to the stockmay then be calculated to give the desired fiber pickup, knowing theconcentration of the resin in the solution which is added to the stock.

After the condensation resin has been introduced into the stock and thepaper laid, the paper is dried at normal paper-drying temperatures andthen it may be compacted by calendering or glazing to obtain maximumdensities. The paper may then be cured, conveniently from aboutone-quarter to about three hours at about 275 to about 409 F. Curingapparently achieves chemical bonding between the resin and the cellulosemolecules as well as cross-linking of the resin. Thus the resinintroduced into the paper becomes an integral part of it and impartspermanent waterproof characteristics to it.

The curing step may be postponed, for the compacted paper may be storedindefinitely and cured at any convenient time or step in laterprocessing or use. Compacting by calendering or glazing may be carriedout after the curing step, although this is not the preferred processorder.

The resulting treated paper after curing is flexible, exhibitsespecially low water absorption and has a very high dielectric strengtheven when exposed to or im- EXAMPLE I Eighty-two grams ofpara-tertiarybutyl phenol (100% 3.0 grams NaOH (96%), 90.4 rams offormalin (37% formaldehyde), 200 grams of water and 200 grams ofisopropyl alcohol were mixed and refluxed for 6 hours at 186 F. Theamount of NaOH present was equivalent to 0.13 mol NaOH for one molpara-tertiary-butyl phenol. The resulting solution of the condensationresin product was cooled and used with no further modification ortreatment.

This solution was added with rapid stirring to the water slurry of the.beater containing 2% by weight refined rag fiber stock. Concentrationswere adjusted so that there were present 33 parts by Weight of resinsolids added to 100 parts by Weight of pulp solids. After the resinsolution and paper stock had been thoroughly emulsified, the resin wasexhausted out onto the fibers by adding paper makers alum (aluminumsulfate). The stock containing the treated fibers was then introducedinto a paper wet dielectric strengths similar to the papers of ExampleI.

A number of other substituted phenols and formaldehyde sources werereacted in varying ratios to give condensation resins suitable fortreating paper to render it waterproof in accordance with the practiceof this invention. Rag paper samples containing from about 5 to about14% or" these resins were then tested for water absorption anddielectric strengths as described in Example l. 7

Methyl alcohol, ethyl alcohol and isopropyl alcohol were used asreaction media and solvents, the isopropyl being preferred for health,safety and economic reasons. The amount of resin solids in the solutionswhich were emulsified in the aqueous paper-making stock varied from 15to by weight. In the example in which HCl was used as a catalyst in thecondensation .reaction, NaOH was added to provide the required amount ofstrongly alkaline materialin the resin solution before it was added tothe paper stock.

The amount of water absorption, based on fiber weight, and the wetdielectric strengths of the paper samples are given in Table 1.

TABLE 1 Water Absorption and .Wet Dielectric Strength Measurements forPaper Samples Treated With Condensation Resins Formed by Reacting aSubstituted Phenol and a Formaldehyde Source Molar Reflux Reflux PercentPercent Wet Substituted Phenol Formaldehyde Ratio, Catalyst Temp, Time,Resin Water Dielectric Source BCHO/ 13. Hrs. Based Absorp- Strength,

C H OH on Fiber tion volts/mil p-oetyl phenol 2:1 NaOH 188 6 p-dodecylphenol- 2:1 NaOH 186 6 dinonyl phen 1:1 NaOH 186 6 p-phenyl phenol 2:1NaOH 182 4 a-phenyl-p-cresoL 2:1 NaOH 182 6 p-cyclohexyl phenol. 2:1 NaOH 180 6 p-nonyl phenol 1:1 NaOH 188 6 p-tertiary-amyl phenol 2:1 NaOH185 6 D0 2:1 NaOH 184 6 Do 2:1 HCl 186 6 p-tertiary-butyl henol d 2:1NaOH 186 5 Do 2:1 NaOH 181 .5 o-secondary-amyl phenol formalin 2:1 N21011 185 4 ((lji-secondary-butyl phenol do 1:1 N 210B 18 5 ontro 1After 4-hour1mmersion in water at 70 F.

machine and a hand sheet of paper made. It was dried on a drum driermaintained at about 220 F. and then cured for one hour at 300 F. Whensamples of this treated paper were immersed in water at 70 F. for fourhours, there resulted 13% water pickup by the treated paper. Thiscompared with 100 to 110% water pickup by an untreated control sample.

Dielectric strengths were measured in accordance with Y thespecifications and method of ASTM test l)-149-55T (Section 15A ShortTime Test). The treated sample of this example had a dry dielectricstrength of 450 volts/ mil and a wet dielectric strength of 200volts/mil compared to 550 volts/ mil and zero, respectively, for theuntreated control. Wet dielectric strength measurements were madeimmediately after the samples were removed from the four-hour waterimmersion.

EXAMPLE [I A condensation resin was made up as in Example I A widevariation in substituted phenols falling within the definition given isillustrated in the above tabulation. Likewise the use of formaldehydesources other than formalin are illustrated in the employment oftrioxane, and the use of an acid catalyst is also shown.

The above table also indicates that dinonyl-phenol, wherein the totalnumber of carbon atoms in the substituent groups is greater than 12, andp-phenyl phenol, which results in the formation of a condensationreaction prodnot having conjugated .unsaturation throughout, areunsuitable. Finally, the unsatisfactory behavior of n-butyraldehyde andparaldehyde is illustrated, due to the fact that they are unable toreact under the operating conditions specified.

The performance of paper treated'in accordance with the practice of thisinvention is further illustrated in FIG. 1 in which percent waterabsorption by the paper is plotted against percent condensation resinbased upon fiber weight. The substituted phenolswere p-tertiarybutylphenoland nonyl-phenol.

The efiect of such treatment on preventing Water absorption by the paperis shovm to increase with increasing amounts of condensation resin untilit is present in the paper from about 4 to 8 percent by fiber weight.Over this amount the increase in hydrophobic properties of the paperbegins to level ofi. This is particularly im- 9 portant since it showsthat a relatively small amount of the condensation resin achieves amarked decrease in water absorption by the paper containing it. Thismeans that the paper retains its flexibility and its other inherentpaper characteristics.

FIG. 2 shows the direct relationship between the amount of waterabsorbed by a paper and its wet dielectric strength. The data in FIG. 2are expressed as ranges since it can be appreciated that theseparameters will vary within a range for difierent materials treated.

From the above examples, tabulation and figures, it will be seen that itis desirable to reduce water absorption particularly in paper to belowabout 30% and preferably to below about 22% if good Wet dielectricstrengths are desired. These figures correspond to about 40 and 100volts/mil, respectively, Wet dielectric strengths. In order to formulatepapers in accordance with this invention, which will exhibit these wetdielectric strengths it is desirable to introduce sufiicient of one ofthe suitable condensation resins so that the resin is present in thepaper in a range from about 2% to 40% by weight of fibers and preferablyfrom about 3% to 12% by weight of fibers.

Paper treated in accordance with the practice of this invention remainsflexible and can be easily handled, folded, cufied for insulationwithout fracturing and can generally be treated as any other normal typeheavy paper. This treated paper is particularly well suited forsplashproof motor insulation and for any other applications where arm'nimum'amount of water should be absorbed by the paper even whencompletely immersed in water.

We claim:

1. An aqueous stock of paper-making fibers, characterized by containingdispersed therein in the form of a discontinuous phase a condensationresin introduced as a solution, said resin being formed by the step ofreacting a formaldehyde source and a substituted phenol under refiuxingconditions at a temperature below about 200 F. to form a condensationresin soluble in acetone,- said substituted phenol having substituentradicals so placed that not more than two methylol radicals of saidformaldehyde source can add to said substituted phenol, said substituentradicals being selected from the group consisting of saturated andunsaturated aliphatic radicals having a total of between 4 and 12 carbonatoms and saturated and unsaturated cyclic hydrocarbon groups which whenjoined to the phenolic ring do not result in the formation of a compoundhaving conjugated unsaturation throughout, said solution of said resincomprising from about 0.05 to one mol of a strongly alkaline materialfor each mol of said substituted phenol present, from about 15 to about35% resin solids by weight of said solution and a mixture of a lowermonohydric alcohol and water as a solvent, the quantity of said water insaid mixture being less than that which will precipitate out said resin.

2. An aqueous stock of paper-making fibers, characterized by containingdispersed therein in the form of a discontinuous phase a condensationresin introduced as a solution, said resin being formed by the step ofreacting a formaldehyde source and a substituted phenol under refluxingconditions at a temperature below about 200 F. to form a condensationresin soluble in acetone, said substituted phenol having substituentradicals so placed that not more than two methylol radicals of saidformaldehyde source can add to said substituted phenol, said substituentradicals being selected from the group consisting of saturated andunsaturated aliphatic radicals having a total of between 4 and 12 carbonatoms and saturated and unsaturated cyclic hydrocarbon groups which whenjoined to the phenolic ring do not result in the formation of a compoundhaving conjugated unsaturation throughout, said solution of said resincomprising from about 0.05 to one mol of a strongly alkaline materialfor each mol of said substituted phenol present,

10 from about 20 to about 25% resin solids by weight of said solutionand a mixture of a lower monohydric alcohol and water as a solvent, thequantity of said water in said mixture being less than that which willprecipitate out said resin.

3. An aqueous stock in accordance with claim 2 wherein said substitutedphenol is nonyl-phenol.

4. An aqueous stock in accordance with claim 2 wherein said stronglyalkaline material is sodium hydroxide.

5. Method of forming a paper stock from which waterproofed paper may beformed, comprising the steps of thoroughly dispersing a solution of acondensation resin in an aqueous paper-making stock containing fibersthereby forming an emulsion of said resin in said stock, said solutionbeing the discontinuous phase of said emulsion, said condensation resinbeing formed by the step of reacting a formaldehyde source and asubstituted phenol under refluxing conditions at a temperature belowabout 200 F. to form a condensation resin soluble in acetone, saidsubstituted phenol having substituent radicals so placed that not morethat two methylol radicals of said formaldehyde source can add to saidsubstituted phenol, said substituent radicals being selected from thegroup consisting of saturated and unsaturated aliphatic radicals havinga total of between 4 and 12 carbon atoms and saturated and unsaturatedcyclic hydrocarbon groups which when joined to the phenolic ring do notresult in the formation of a compound having conjugated unsaturationthroughout, said solution of said resin comprising from about 0.05 toone mol of a strongly alkaline material for each mol of said substitutedphenol present, from about 15 to about 35% resin solids and a mixture ofa lower monohydric alcohol and Water as a solvent, the quantity of saidwater in said mixture being less than that which will precipitate outsaid resin.

6. Method of making a waterproofed paper, comprising the steps ofthoroughly dispersing a solution of a condensation resin in an aqueouspaper-making stock containing fibers thereby forming an emulsion of saidresin in said stock, said solution being the discontinuous phase of saidemulsion, said condensation resin being formed by the step of reacting aformaldehyde source and a substituted phenol under refluxing conditionsat a temperature below about 200 F. to form a condensation resin solublein acetone, said substituted phenol having substituent radicals soplaced that not more than two methylol radicals of said formaldehydesource can add to said substituted phenol, said substituent radicalsbeing selected from the group consisting of saturated and unsaturatedaliphatic radicals having a total of between 4 and 12 carbon atoms andsaturated and unsaturated cyclic hydrocarbon groups which when joined tothe phenolic ring do not result in the formation of a compound havingconjugated unsaturation throughout, said solution of said resincomprising from about 0.05 to one mol of a strongly alkaline materialfor each mol of said substituted phenol present, from about 15 to about35 resin solids and a mixture of a lower monohydric alcohol and water asa solvent, the quantity of said water in said mixture being less thanthat which will precipitate out said resin, acidifying said emulsionwhereby said resin is exhausted out onto said fibers, introducing theresulting stock to a paper machine to form paper, and drying said paper.

7. Method of making a Waterproofed paper, comprising the steps ofthoroughly dispersing a solution of a condensation resin in an aqueouspaper-making stock containing fibers thereby forming an emulsion of saidresin in said stock, said solution being the discontinuous phase of saidemulsion, said condensation resin being formed by the step of reacting aformaldehyde source and a substituted phenol under refluxing conditionsat a temperature below about 200 F. to form a condensation resin solublein acetone, said substituted phenol having substituent radicals soplaced that not more than two methylol radicals of said formaldehydesource can add to said from the group consisting of saturated andunsaturated aliphatic radicals having a total of between 4 and 12 carbonatoms and saturated and unsaturated cyclic hydrocarbon groups which whenjoined to the phenolic ring do not result in the formation of a'compoundhaving conjugated, unsaturation throughout, said solution of said resincomprising from about 0.05 to one mol of a strongly alkaline materialfor each mol of said substituted phenol present, from about 15 to about35% resin solids and a mixture of a lower monohydric alcohol and wateras a solvent, the quantity of said water in said mixture being less thanthat which will precipitate out said resin, acidifying said emulsionwhereby said resin is exhausted out onto said fibers, introducing theresulting stock to a paper machine to form paper, drying said paper, andcuring it 7 at temperatures ranging between 275 and 400 F.

8. Method in accordance with claim 7 including the step of compactingsaid paper subsequent to said drying to maximize its density.

9. A condensation resin product suitable for adding to papermaking stockto render the resulting paper made therefrom waterproof, said resinbeing formed-by the steps of reacting a formaldehyde source and asubstituted phenol for from about one-half to about ten hours in a loweralcohol in the presence of a catalyst at temperatures between about 150and 200 F. under refluxing conditions to form a' condensation resinsoluble in acetone, said formaldehyde source and said substitutedphenols being present in molar ratios ranging from about one-half mol offormaldehyde to one mol of said substituted phenol to about two mols offormaldehyde to one mol of said substituted phenol, said substitutedphenol having substituent radicals'so placed that not more than twomethylol radicals of said formaldehyde source can add to saidsubstituted phenol, said substituent radicals being selected from thegroup consisting of saturated and unsaturated aliphatic radicals havinga total of between 4 12 11. Condensation resin product in accordancewith claim 9 wherein said formaldehyde source is formalin. 12. Awaterproof paper characterized by having cheruically bonded tosubstantially all of the fibers thereof a condensation resin present inan amount ranging from about 2 to about 40% by fiber Weight, said resinbeing formed by reacting a formaldehyde source and a substituted phenolunder refluxing conditions at a temperature below about 200 F to form acondensation resin soluble in acetone, said substituted phenol havingsubstituent radi cals so placed that not more than two methylol radicalsof said formaldehyde source can add to said substituted phenol, saidsubstituent radicals being selected from the group consisting ofsaturated and unsaturated aliphatic radicals having a total of between 4and 12 carbon atoms and saturated and unsaturated cyclic hydrocarbongroups which when joined to the phenolic ring do not result in theformationof a compound having conjugated unsaturation throughout, saidresin being introduced in said paper by the steps of thoroughlydispersing a solution of said resin in an aqueous paper making stockcontaining fibers thereby forming an emulsion of said resin in saidstock, said solution of said resin comprising from about 0.05 to one molof a strongly alkaline material for each mol of said substituted phenolpresent, from about 15 to 35% resins solids and a mixture of a lowermonohydric alcohol and water as a solvent, the quantity of said water insaid mixture being less than that which will precipitate out said resin;acidifying said emulsion whereby said resin is exhausted onto saidfibers, introducing the resulting stock into a paper machine to formsaid paper, and drying said paper.

13. Paper formed in accordance with claim 12 wherein said fibers arerefined rag fibers formed into a dense sheet.

References Cited in the file of this patent UNITED STATES PATENTS2,441,860 Whetstone May 18, 1948 2,563,614 Palmer Aug. 7, 1951 2,639,242Suen May 19, 1953 2,809,178 Turner et al. Oct. 8, .1957 2,811,508Kleincke Oct. 29, 1957 2,827,121 Nowak Mar. 18, 1958 2,894,931Somerville et al. July 14, 1959

5. METHOD OF FORMING A PAPER STOCK FROM WHICH WATERPROOFED PAPER MAY BEFORMED, COMPRISING THE STEPS OF THOROUGHTLY DISPERSING A SOLUTION OF ACONDENSATION RESIN IN AN AQUEOUS PAPER-MAKING STOCK CONTAINING FIBERSTHEREBY FORMING AN EMULSION OF SAID RESIN IN SAID STOCK, SAID SOLUTIONBEING THE DISCONTINUOUS PHASE OF SAID EMULSION, SAID CONDENSATION RESINBEING FORMED BY THE STEP OF REACTING A FORMALDEHYDE SOURCE AND ASUBSTITUTED PHENOL UNDER REFLUXING CONDITIONS AT A TEMPERATURE BELOWABOUT 200*F. TO FORM A CONDENSATION RESIN SOLUBLE IN ACETONE, SAIDSUBSTITUTED PHENOL HAVING SUBSTITUENT RADICALS SO PLACED THAT NOT MORETHAN TWO METHYLOL RADICALS OF SAID FORMALDEHYDE SOURCE CAN ADD TO SAIDSUBSTITUENT PHENOL, SAID SUBSTITUENT RADICALS BEING SELECTED FROM THEGROUP CONSISTING OF SATURATED AND UNSATURATED ALIPHATIC RADICALS HAVINGA TOTAL OF BETWEEN 4 TO 12 CARBON ATOMS AND SATURATED AND UNSATURATEDCYCLIC HYDROCARBON GROUPS WHICH WHEN JOINED TO THE PHENOLIC RING DO NOTRESULT IN THE FORMATION OF A COMPOUND HAVING CONJUGATED UNSATURATIONTHROUGHOUT, SAID SOLUTION OF SAID RESIN COMPRISING FROM ABOUT 0.05 TOONE MOL OF A STRONGLY ALKALINE MATERIAL FOR EACH MOL OF SAID SUBSTITUTEDPHENOL PRESENT, FROM ABOUT 15 TO ABOUT 35% RESIN SOLIDS AND A MIXTURE OFA LOWER MONOHYDDRIC ALCOHOL AND WATER AS A SOLVENT, THE QUANTITY OF SAIDWATER IN SAID MIXTURE BEING LESS THAN THAT WHICH WILL PRECIPITATE OUTSAID RESIN.